1. Field of the Invention
The present invention relates to an X-ray CT apparatus which has a compact and lightweight structure in comparison with the conventional X-ray CT apparatus.
2. Description of Related Art
There is a known X-ray CT apparatus of a so-called "helical-scanning" type, as shown in FIG. 1. The shown X-ray CT apparatus includes a frame 100 in the form of a box. Disposed at the center of the frame 100 is a radiographic port 101 into which a patient laid on a not-shown bed is to be inserted. About the radiographic port 101, an X-ray tube and an X-ray detector opposing thereto are adapted so as to rotate along the periphery of the port 101 together with a part of power processing components and signal processing components, providing a rotating part 102. In operation, by irradiating X-ray against the patient inserted into the radiographic port 101 while the rotating part 102 rotates, the X-ray apparatus is so constructed as to pick up an image of tomographic layer of a desired part of the patient. Further, the frame 100 is provided, on a bottom part 100a thereof, with a suction port 103. On an upper part 100b of the frame 100, cooling fans 104b are disposed to discharge air sucked through the suction port 103 for circulating the interior of the rotating part 102, thereby cooling down the X-ray tube and power circuits etc. which are heated by scanning.
The interior constitution of the frame 100 are shown in FIGS. 2A and 2B.
In the rotating part 102, a rotary base 110 is equipped with the X-ray tube, the X-ray detector and a high-voltage generator. The rotary base 110 is arranged on a fixed base 112 through the intermediary of a bearing 111.
A drive motor 113 for rotating the rotating part 102, and electric components 114a to 114c, such as baseplates and power circuits, for controlling a dose of X-ray and other parameters are arranged on the fixed base 112. Due to the weightiness of the drive motor 113, it is disposed on a lower part of the frame 100. The electric components 114a, 114b are arranged on both shoulders of the frame 100, while the component 114c is provided on the lower part of the frame 100. Thus, as a natural result of the above-mentioned arrangement of the electric components 114a, 114b on both shoulders of the frame 100, a cover 117 for covering the whole of the frame 100 is shaped in the form of a box.
The fixed base 112, the drive motor 113 and the electric components 114a to 114c constitute a fixed part of the apparatus. By a stand 115 through tilting supports 116, the fixed part is carried so as to tilt by predetermined angles. Owing to this arrangement, it is possible for the whole frame 100 to tilt about the supports 116 as fulcrums by the predetermined angles, thereby allowing the apparatus while tilting the frame 100 to scan the patient.
From FIG. 2B where the frame 100 is viewed from its wiring side, it will be understood that a power line 120 approaches the interior of the apparatus by way of the backside of the frame 100. This is because the not-shown bed for mounting the patient is provided on the front side of the frame 100.
The power line 120 is connected to the rotating part 101 and the electric components 114a to 114c of the fixing part through the intermediary of various kinds of breakers and electric filters in the stand 115. Of course, in the rotating part 110, the electric power is supplied to the high-voltage generator and the X-ray detector through so-called "slip rings" (not shown).
Next, a signal line 121 for transmitting various control signals from console units or the like is wired by the way of the backside of the frame 100, as similar to the above-mentioned power line 120. Being wired side by side with the power line 120 as shown in FIG. 2B, the signal line 121 is also connected to the electric components 114a to 114c. Further, the signal line 121 for transmitting signals processed by the electric components 114a to 114c is divided into a signal branch line for controlling the drive motor 113 and signal branch lines for controlling the action of the bed and the X-ray system. It is noted that radiographic (pick-up) signals generated by the X-ray detector are transmitted to the console units through optical transmitting parts arranged in the rotating part 102 and the fixed part.
By the way, it should be noted that the X-ray CT apparatus and the other medical instruments have been developed in performance for recent years and their applications have been enlarged with the improvement of performance. Additionally, being involved in an information-oriented society, the above-mentioned medical instruments have been subjected to the application of electronic instruments, such as moving telephones.
Therefore, there has been caused a problem that the medical instruments operate erroneously due to radio waves and noises produced from the electronic instruments. Under such a situation, it is eagerly required to prevent the noise from generating from the medical instruments and avoid their erroneous operation.
In the above-mentioned prior art X-ray CT apparatus, however, it has a problem of increasing the length of wiring since the power line 120 and the signal line 121 have to be wired to various parts through the stand 115 and the supports 110 in order to allow the tilting operation of the frame 100. Consequently, there is a possibility of picking up unnecessary internal and external radio waves or noises due to the electrical wiring of the power line 120 and the signal line 121 etc. acting as antennas. Thus, the longer the wiring length of the medical instrument becomes, the broader the instrument can pick up the radio waves and the noises disadvantageously. Especially, since there is established a severe standard about the electromagnetic noise in IEC (international electrotechnical comission) standard which is an international standard for electrical instruments, it is required to take strong measures to cope with the IEC standard.
In addition, since the electric components 114a to 114c of the prior art X-ray CT apparatus are dispersed in the frame 100, it is difficult to take the measures for electromagnetic noise and the assembling process is apt to be complicated. Further, in assembling of the apparatus, the arrangement of the electric components 114a to 114c requires spaces for the establishment of the components 114a to 114c. Thus, the conventional X-ray CT apparatus has a problem that it is large-sized due to the frame 100 in the form of a box. Such a large-sized apparatus is apt to overawe the patient to be inspected and makes it difficult to ensure a space required for establishing the apparatus in a hospital.
When taking the tomography image of the patient by the oblique scanning in the conventional X-ray CT apparatus, the whole frame 100 is tilted as shown in FIG. 3. In such a case, there is a possibility that an operator's operations to adjust the position of the patient and to puncture etc. are interrupted by the projecting lower part of the slanted frame 100, thereby causing a great hindrance to the operator working about the apparatus.